The present invention relates to robot controls and more particularly to robot controls implemented with digital technology to produce better performance for multiaxis robots.
The design of robot controls has been based in part on what has been learned from the design of numerical machine tool controls. In a typical machine tool control, a position control loop may be implemented in a microprocessor or other digital controller which generates an analog voltage representing a velocity setpoint for a power amplifier assembly. Servo control loops for velocity and torque are closed typically with analog circuitry located within the power amplifier assembly.
In more recent robot controls, both position and velocity control loops have been implemented in a microprocessor or other digital controller which generates a voltage output representing velocity error or current setpoint for the power amplifier assembly. Analog circuitry in the power amplifier closes the current loop.
Requirements placed on robot control systems differ significantly from those placed on numerical machine tool controls. The following are two basic differences:
1. Control loop parameters can typically be established to optimize control at the time of machine tool installation because time constants for the system are relatively constant for all operating conditions of the machine. Robot control parameters cannot be similarly fixed since robot time constants can vary significantly over the operating range of the robot arm due to large inertia changes caused by the manipulation of variable weight loads from fully collapsed to fully extended arm positions.
2. Machine tools typically require stiff accurate path control. Robot arms typically require dexterity which in turn can require control over the force applied by the robot arm to an object.
Apart from these unique operating requirements, robot controls have been lacking in design adaptability to accommodate advancing robot technology with convenience and economy. They have further been lacking in design adaptability to be operable with high universality in meeting varied customer applications having different cost, robot performance and system requirements.
With a completely digital control configuration, all of the foregoing special robot control needs can be more readily and more effectively met through better robot performance enabled by digital capabilities and better design adaptability enabled by digitally facilitated modular hierarchical organization. The present invention is directed to the overall configuration of a new substantially completely digital robot control which meets these objectives. The referenced patent applications are directed to various aspects and features of the new digital robot control.